add references

Author: astorfi

setup.py

@@ -1,12 +1,12 @@
 from setuptools import setup, find_packages
 
 setup(name='speechpy',
-      version='2.3',
+      version='2.3.1',
       description='The python package for extracting speech features.',
       author='Amirsina Torfi',
       author_email='amirsina.torfi@gmail.com',
       url='https://github.com/astorfi/speechpy',
-      download_url = 'https://github.com/astorfi/speechpy/archive/2.3.zip',
+      download_url = 'https://github.com/astorfi/speechpy/archive/2.3.1.zip',
       packages=find_packages(exclude=('tests', 'docs')),
       include_package_data=True,
       install_requires=[